1. Field of the Invention
This invention relates to a semiconductor device manufacturing apparatus for forming an insulation film on a semiconductor substrate, and more particularly to a sputtering chamber structure in which a high-frequency bias sputtering process is effected to form the insulation film.
2. Description of the Related Art
In a multi-layered wiring process for a semiconductor device, an interlayer insulation film is formed by using a single wafer type high-frequency bias sputtering device, for example. The high-frequency sputtering device is used to effect sputtering onto a semiconductor wafer substrate including a plurality of partially fabricated semiconductor devices so as to form a relatively thick single insulation film as interlayer insulation films of the semiconductor devices. The sputtering process is effected by bombarding particles such as Ar.sup.+ ions onto a target material and depositing resulting particles emitted from the target material on a semiconductor wafer substrate placed on the opposite side thereof. In the process, Ar.sup.+ ions also bombard the semiconductor substrate so that the substrate can have a smooth surface. In recent bias sputtering devices, a permanent magnet or electromagnet is provided on the rear side of the target plate and the distance between the semiconductor wafer substrate and the target plate is reduced to several tens of mm so that the film formation speed can be enhanced.
FIG. 1 is a cross sectional view showing the sputtering chamber structure of the conventional single wafer type high-frequency bias sputtering device dedicated to the formation of an insulation film. The sputtering device has target electrode 13 to which target 14 is attached. Semiconductor wafer substrate 18 is first placed at a position opposite target 14 in the sputtering chamber SR, placed on substrate electrode 17 and then pivoted as shown by an arrow in FIG. 1. As a result, when substrate electrode 17 is disposed to face target 14, the surfaces of the substrate electrode and the target are parallel to each other. After this, a first high-frequency power is applied between target electrode 13 and chamber wall 11, and a second high-frequency power is applied between substrate electrode 17 and chamber wall 11.
In the sputtering device, metal protection plate 16 is formed along the outer peripheral portion of target 14 in order to block those sputtered particles which are not deposited on semiconductor wafer substrate 18. However, metal protection plate 1 cannot block all of such particles, and it is impossible to prevent sputtered particles from being deposited on the chamber wall 11 of sputtering chamber SR.
FIG. 2 shows an example of an empirically modified metal protection plate 21 of the sputtering device shown in FIG. 1. In this case, target 14 is surrounded by metal protection plate 21 having an opening in a portion facing target 14. The opening is substantially closed by means of substrate electrode 17 when semiconductor wafer substrate 18 is disposed facing target 14.
However, when metal protection plate 21 is used to prevent the sputtered particles from being deposited on chamber wall 11 of sputtering chamber SR, plasma (for example, of Ar ions) will be concentrated in the gap 22 between electrode 17 and metal protection plate 21. As a result, the sputter-etching rate in a partial area of semiconductor wafer substrate 18 at which plasma density is high is increased. For this reason, an insulation film formed on semiconductor wafer substrate 18 tends to have nonuniform thickness.
In the case where a 5-inch substrate 18 is used and disposed at a distance of 60 mm from target 14 and at a distance of 5 mm from metal protection plate 21 having an opening of 140 mm diameter, an insulation film was formed on substrate 18 by effecting the sputtering process under the following conditions: Ar partial pressure was at 0.30 pa, Ar flow rate was 30 SCCM, the target power was 3.0 kW, the substrate power was 0.5 kW, and a permanent magnet for generating a magnetic field having a field component parallel to and near the surface of cathode plate 13 was used. Curve b in FIG. 3 shows the results of measuring the film formation speeds for each of the portions of semiconductor wafer substrates 18 which were spaced from the peripheral edge by more than 5 mm and are in a single line extending across the center of substrate 18. In this case, the film formation speed was 80 nm/min, and the uniformity of the speed of sputtering for the substrate varied within a range of .+-.40% as shown by curve b in FIG. 3. Further, in the case where metal protection plate 21 was not provided, the film formation speed and the uniformity of sputtering speed were 95 nm/min and .+-.5% as shown by curve a in FIG. 3. Thus, in this case, good uniformity was obtained. Twenty five semiconductor substrates 18 were each subjected to the film formation process for 10 minutes under the same conditions as described before but without using protection plate 21. Then, another substrate 18 was horizontally positioned in a reduced-pressure Ar atmosphere before effecting the film formation process. A particle check was effected before and after film formation by sputtering. As shown by point d in FIG. 4, approx. 8000 particles of 0.3 .mu.m or more in diameter were deposited on the last substrate 18 as dust. The number is relatively large when considering that only 60 particles were present before the film formation was effected. This is mainly because the sputtered film formed on chamber wall 11 is removed by temperature variation. If such a large number of particles are deposited on substrate 18, the particles will be included in a film formed in a succeeding sputtering process. Therefore, a decrease in the breakdown voltage, an increase in the film leakage current, and short circuit(s) in the upper wiring layers may be caused and the reliability will be lowered.